Hey im lookin for a new snowboard that will be good all-mountain freeride , good in park and pow. I am looking at a Gnu DK Dirty habits Is this a good board for my type of riding i want to do. I am open for any suggestions or opinions on this board or any others.
would a 155 be a good size for me or should i go go 158?

I just bought a Rome Agent as all mountain board, it gets great reviews here. I received it but I have not yet tried it so I can not tell you more about it. But many members here recommeded the board for all mountain riding with great park capabilities. Do a search for it.

As far as the size, it depends on what you like. I tend to buy boards at the shorter end of my range, as I like to have more control over my board than high speed. If you are planning to him more powder I would recommend to buy a longer board, but if you are more orientated towards park go towards the shorter board.